This is a long standing study of 30 years duration of a large kindred with 131 members, some of whom have the hereditary form of thyroid and adrenal cancer. Screening of family members with a calcium/pentagastrin infusion and linkage mapping using restriction fragment length polymorphism in this study has linked the gene to the centromere of chromosome #10. This data is now being correlated with definitive PcR analysis for mutating in the RET gene.